The present invention relates to reference voltage supply circuits for providing a regulated direct current output voltage and, more particularly, to a temperature compensated integrated voltage regulator circuit including means for compensating beta variations in transistor elements comprising the circuit due to semiconductor process variations.
Integrated temperature compensated regulator circuits for providing a D.C. voltage reference that can be utilized to bias ECL circuits, for instance, are well known in the art. Temperature compensation is provided by operating a pair of transistors at different current densities to establish a difference in the base-emitter voltages, .DELTA.V.sub.BE, between the emitters of the two transistors and establishing a current therefrom having a positive temperature coefficient. This current is then utilized to produce a voltage in series with the negative temperature coefficient of the base-emitter voltage of a third transistor to establish the temperature compensated reference voltage.
U.S. Pat. No. 3,781,648 discloses a voltage regulator of the above mentioned type further including means for compensating for variations in beta of the transistor elements incurred as a result of process variations in the integrated circuit fabrication processes. As will be more fully explained later, this circuit is comprised of a resistor disposed in the base circuit between the first and second transistors that are operated at different current densities to reduce variations of the reference voltage as the beta of the transistors varies due to process variations, which in turn causes the V.sub.BE and base currents of the transistors to vary.
Although the aforementioned regulator works quite well, there is a need for a similar type regulator having improved beta compensation means required in today's higher performance circuit designs.